Heating oil-bearing formations



Nov. 9, 1965 J. w. PALM 3,216,493

HEATING OIL-BEARING FORMATIONS F'v' led June 22, 1962 2 Sheets-Sheet 1 AIR- REACTION l CHAMBER INVENTOR.

J.W. PALM ATTORNEY Nov. 9, 1965 J. w. PALM HEATING OIL-BEARING FORMATIONS 2 Sheets-Sheet 2 Filed June 22. 1962 FUEL PLUS AIR TO FORMATION FIG. 3

PREHEAT SECTION EACTION SECTION INVENTOR.

a. w. PALM J7 ATTORNEY FIG. 2

3,216,498 HEATING GIL-BEARING FORMATIONS John W. Palm, Tulsa, Okla assignor to Pan American Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Filed June 22, 1962, Ser. No. 204,423 12 Claims. (Cl. 166-38) This invention is directed to a method for heating the face of a hydrocarbon-containing formation penetrated by a well. More particularly, it is concerned with a procedure by which the face of said formation can be heated at a moderate, controlled temperature. Specifically, the method of this invention is based on the fact that hydrocarbons can be partially oxidized at relatively low temperature, i.e., below about 1200" F. Such method involves conducting this partial oxidation step in the well opposite the formation to be heated or to be subsequently ignited.

Previous methods of igniting oil-bearing formations in preparing them for underground combustion have not met with unqualified success. One of the principal difficulties has been that in the course of heating the formation to ignition temperature, the casing or screen as well as any other equipment in the vicinity of the heated zone is damaged by the excessive temperatures generated. In fact, the temperatures produced have been so high that the burner itself was considered an expendable item. In other instances, electrical heaters have been employed for ignition and for the control of paraflin deposition. However, they are subjct to a number of practical problems, including shorting out, and in some instances they have been lost in the hole. Unlike the gas or liquid fuel burners, electrical heaters are not considered expendable and the loss of such equipment represents a cost of several thousand dollars.

It is another object of my invention to provide a method for conducting a relatively low temperature combustion procedure which can be used to initiate underground combustion or to prevent the occurrence of objectionable paratfin deposits in a Well. It is a still further object of my invention to control the temperature of the products of combustion formed in this partial oxidation process through the heat exchange of hot combustion products with a cooler stream of reacting gases prior to said products contacting the formation face.

In the drawings, FIGURE 1 is an elevational view, partially in section, of a burner design suitable for conducting the partial oxidation of a hydrocarbon fuel under conditions such that temperatures not in excess of about 1200 F. are generated.

FIGURE 2 is another burner design which may be employed in carrying out the partial oxidation step in accordance with my invention and is similar in principle to the structure shown in FIGURE 1.

FIGURE 3 is a design of apparatus which controls the temperature of the products of combustion primarily through effecting direct heat exchange in a suitable reaction chamber between hot product gases and cooler reactants.

In carrying out my invention, air or other suitable oxygen-containing gas is injected into a well penetrating an unheated oil-bearing formation which it is desired to ignite, A suitable fuel such as natural gas, butane, gasoline, etc., is mixed with air either prior to reaching the area to be heated or at a level substantially opposite said formation. The temperature at which the partial combustion proceeds is controlled in large part by the composition of the air-fuel mixture. In carrying out the process of my invention, the maximum temperature developed in the burner or heating apparatus rarely exceeds about 1000 F. Minimum temperatures attained United States Patent ice by the combustion products themselves are generally of the order of about 500 to 700 F. and while these values may be reached by the combustion of either air-rich or hydrocarbon-rich mixtures, I generally prefer to employ air-rich streams since they are less costly. The combustible mixtures used in heating the formation may be ignited by any of a number of well-known means, such as by the use of a pyrophoric material, a hot wire, sparkplug, etc.

In controlling the temperature of the hot zone within a range of, for example, 600 to about 1000 F. using air-rich mixtures, the air and fuel, for example butane hydrocarbon, should be employed in an amount ranging from about 106 pounds of air per pound of fuel to about 19 /2 pounds of air per pound of fuel.

In the case of hydrocarbon-rich mixtures, air-fuel ratios-again using butane fuel as an example-suitable for generating temperatures within the above-stated range vary from about .93 pound per pound of butane to about 0.155 pound per pound of butane.

In heating the formation face in accordance with my invention, flow rates should generally be such that the residence time of the gases in the reaction section of the apparatus varies from about 0.5 to about 300 seconds, depending on whether the reaction mixture is air-rich or hydrocarbon-rich. Due to their faster reaction rate, the higher molecular weight fuels may be used with shorter residence time than the lighter materials.

The pressures employed in carrying out my invention may vary widely. However, in general, the efiiciency of the process improves with increasing pressure. Thus, the partial oxidation involved herein may be carried out at pressures ranging from atmospheric to several thousand pounds per square inch. At the high pressures, lower temperatures and shorter residence times may be used. In this connection, it should be pointed out that during the partial oxidation or heating process some chemicals, such as aldehydes and alcohols, are formed. However, the amount of these materials is small and in no way tends to interfere with bringing the temperature of the formation face to the desired level.

To further illustrate the reaction conditions employed both in the case of air-rich and butane-rich mixtures, the ranges of air-fuel mixtures, residence times, pressures which may be employed, etc., are included in the table appearing below.

Table Fuel Mixtures Operating Conditions, Air-Fuel Ratio, lb./lb.

Air-Rich Hydrocarbon- Rich Using natural gas Using normal butane Using gasoline Air-fuel ratio, percent of theoretical Residence time, see 0 Pressure, p.s.i.g Reaction temperature range, F- Pr ell i eat temperature of fuel mixture.

Referring now to FIGURE 1, one embodiment of the apparatus contemplated by my invention comprises a lower portion of a tubing string 2 having a landing nipple 3 holding a plug 4. A fuel line 6 is threadedly engaged to plug 4 and the contents thereof mix with an air stream travelling down the tubing and into channel 8. A tube 10 is threadedly connected to the underneath side of plug 4 and takes the mixture of air and fuel down into a coiled section 12 and on up tubing 10 to outlet 14 thereof. The mixture emerging from outlet 14 is ignited by means of spark plug 16 inserted through a channel in plug 4. The resulting ignited mixture flows downwardly through combustion chamber or reaction section 18 and around coils 12 serving to preheat the mixture of air and fuel in said coils moving toward outlet 14. The hot products of partial combustion then flow out the bottom of the heater and contact the sides of the formation face. Actually, the portion of the tubing below plug 4 need not be used since the well casing or the open hole tend to serve essentially the same purpose.

This particular structure renders the apparatusshown in FIGURE 1 extremely versatile because the actual temperature of the gas emerging from thecombustion zone may range from about 300 to about 1000 F. This is true because in heat exchanging the hot gases in reaction section 18 with the cooler reactants in coils 12, the reactants are preheated to reaction temperature and the products of partial combustion are cooled substantially. As indicated above, depending on the composition of the reactant mixture, the temperature of the.

gas finally contacting the well wall can be made to vary over an extremely Wide range. It should also be pointed out that the size of coil section 12 and, of course, the temperature of the air and gas aifect' the temperature of combustion products discharged into the well. Accordingly, the principal of my invention is not only useful for the purpose of heating the formation face to a temperature that will cause the establishment of a burning front in the presence of excess air, but this phenomenon can also be taken advantage of in adapt-i ing it to bottom hole heating. Thus, if the temperature of these gaseous products" of combustion can be held to'a level of from about 300 to about 600 F., as mentioned above, it will be realized that paraffin deposited on the formation wall and/ or in the tubing can be successfully removed by thisnovel heating method and means. In the case of the embodiment shown in FIGURE 1, as well as that illustrated in FIGURE 2, the burner may be operated periodically or continuously at a low, e.g. 300 F., temperature level where it is desired to combat paraffin deposition. If operated periodically, the apparatus may be permitted to remain in place or, if desired, may be withdrawn from the 'well.

The embodiment shown in FIGURE "2 is a modification of the apparatus of FIGURE 1-, in whichthe coiled portion 12 of tubing 10 is adjacent plug 4 and terminates about halfway down the portion of tubing I string 2 extending below plug 4. Thus, it will be seen 1 that coiled section 12 in essence terminates at plate 20 resting at 21 in seating nipple 23. Plate 20 divides the tubing below plug 4 into a preheat section and a reaction section. The exhaust from tubing 10 flows into reaction section 22 where the air-fuel mixture is ignited by means of spark plug 16. The reaction mixture, as it comes from coil 12 into section 22 may be at temperatures of from"'400 to 700 F. and on ignition and reaction under conditions of partial oxidation reachesia temperature in section 22 typically of the order of about 800 to 1000 F. Of course, once the reaction section has reachedthis temperature level,

further ignition by auxiliary means is unnecessary because gases coming from the coil or entering section 22 are rapidly brought to reaction temperatures of 800 to 1000 F. as the result of thermal mixing. Hot reaction products are removed from section 22 via dip tube 24 and enter heat exchange section 26 at 800 to 1000 F., serving to heat the fuel mixture, entering coil 12 at about 100 R, up to a level of 400 to 700 F. The product gases in section 26, after giving up a sub stantial amount of their heat, flow out into the well annulus via ports 28 and contact the casing or open hole, not shown, thereby raising the temperature of the formation to a level at which it will ignite on contact with air or a similar oxygen-containing gas; .Here v 28 can be controlled by varying the composition of the reaction mixture flowing through pipe 10, or as otherwise explained herein. As in the case of FIGURE 1, the apparatus shown in FIGURE 2 likewise may be used as a bottom hole heater with appropriate changes in composition of the reactant gases, as taught above.

FIGURE 3 is still another modification in which mixing of reactants coming down line 30 is achieved by flowing them into an open-ended reaction chamber 32. Thermal mixing occurs in the reactor due to eddies of the hot product gas which rise into and mix with the enteringreactants. With a reaction zone of this kind, mixing of reactants and reaction products is accomplished, thereby effecting good preheating of the reactants to the temperature required for partial combustion or oxidation. Combustion products at a temperature of, for example, 600 to 1000 F. issue from the base of reaction. chamber 32 and directly or indirectly heat the adjacent formation. Actually, casing 36 may be a screen placed against the producing formation, or the formation may be open and unprotected. In any event, when theformation face has been heated over a desired area to a temperature of, for example, 400 to 1000 F., the burner is withdrawn from the well and air injection at the required rate is begun. If forward combustionis to be conducted, such air injection step is carried out in the ignition well. If reverse combustion is to be performed, air is injected in a nearby offset well. Air injection in the case of reverse combustion may be conducted simultaneously with the heating step occurring in the producing well.

I claim? 1."A method for heating the face of an oil-bearing formation penetrated by a well which comprises:

partially oxidizing" a fluid hydrocarbon in a reaction zone atalevel in said well substantially opposite said formation with suflicient oxygen-containing gas to produce products from this partial oxidation having a temperature ranging from about 600 to about 1000 F., the residence time of the reactants in said zone ranging from about 0.5 to about 300 seconds, passing said productsin indirect heat exchange relation with an, oxygen-containing mixture of a fluid hydrocarbon which is to be subsequently partially oxidized in said reaction zone to preheat said mixre nd withdrawing said products from said zone and heating said formation therewith. V 2. The process of claim 1 in which the fluid hydrocarbon is a normally gaseous hydrocarbon.

3. The process of claim 1 in which the fluid hydrocarbon a butane and the air-butane ratio employed ranges from about 0.155 pound of air per pound of butane to 0.93poundof air per pound of butane.

4. The process of claim 1 in which the fluid hydrocarbon is a normally liquid hydrocarbon.

5. The process of claim 1 in which the hydrocarbon component is gasoline.

6. A method for heating the face of an oil-bearing formation penetrated by a well which comprises:

partially oxidizing a'fluid hydrocarbon .ina reaction zone at a temperature ranging from about 600 F. to about 1000 F.; at a level in said well substantially opposite said formation with sufficient oxygencontaining gas to produce products from this partial oxidation, I passing said products in indirect heat exchange relation with an oxygen-containing mixture of a fluid hydrocarbon which is to be subsequently partially oxidized in said reaction zone to preheat said mixture, withdrawing said products from said zone and heating said formation therewith, and subjecting said mixture to partial oxidation, said mixture having suflicient oxygen to produce products within the aforesaid temperature range.

7. A method for heating the face of an oil-bearing formation penetrated by a Well which comprises:

introducing a mixture having as its essential components oxygen and a fluid hydrocarbon which is to be subsequently partially oxidized into a zone having a preheat section and a reaction section, heating said mixture to a minimum temperature of from about 100 to about 700 F.,

next subjecting said mixture to partial oxidation in said reaction section and controlling the reaction temperature within a range of from about 600 to about 1000 F.,

thereafter passing the hot products of said partial oxidation in indirect heat exchange relation with a cooler oxygen-fluid hydrocarbon mixture in said preheat section,

next withdrawing said products from said preheat section, and contacting said formation with said products. 8, A method for controlling paraflin deposition in a well penetrating an oil-bearing formation which comprises:

preheating a mixture having as its essential components oxygen and a fluid hydrocarbon to a temperature of about 100 to about 700 F.,

next subjecting said mixture to partial oxidation in a reaction zone at a level in said well substantially opposite said formation with sufficient oxygen to produce oxidation products at a temperature of from about 600 to 1000 F.,

next passing these oxidation products in indirect heat exchange with a cooler oxygen-fluid hydrocarbon mixture being introduced into said reaction zone,

thereafter withdrawing said products from said zone at an elevated temperature not in excess of about 600 F., and

contacting said paraflin with said products.

9. The process of claim 8 in which the fluid hydrocarbon employed is a butane.

10. The process of claim 8 in which the fluid hydrocarbon employed is a normally gaseous hydrocarbon.

11. The process of claim 8 in which the fluid hydrocarbon employed is a normally liquid hydrocarbon.

12. The method of heating an oil-bearing formation penetrated by a well which comprises:

introducing a mixture having as its essential components oxygen and a fluid hydrocarbon which is to be subsequently partially oxidized into a reaction zone at a level in said well substantially opposite said formation, the amount of oxygen in said mixture being such that partial oxidation of said hydrocarbon occurs at a reaction temeprature of from about 600 to about 1000 E, immediately thereafter thoroughly mixing the resulting products of such partial oxidation with a cooler oxygen-fluid hydrocarbon mixture being introduced into said reaction zone, and withdrawing from said zone products of partial oxidation at an elevated temperature not substantially in excess of about 600 F.

References Cited by the Examiner UNITED STATES PATENTS 797,529 8/05 Oliphant et a1. 16639 2,225,775 12/40 Garrett 16659 2,887,160 5/59 De Priester et a1. 16659 2,890,755 6/59 Eurenius et al. 16659 2,985,240 5/61 Emery 166-59 3,018,827 1/62 Henderson et al. 16639 3,026,937 3/62 Simrn- 16639 3,072,191 1/63 Bond et a1. 16639 3,126,954 3/64 Campion 16611 BENJAMIN HERSH, Primary Examiner. 

3. A METHOD FOR HEATING THE FACE OF AN OIL-BEARING FORMATION PENETRATED BY A WELL WHICH COMPRISES: PARTIALLY OXIDIZING A FLUID HYDROCARBON IN A REACTION ZONE AT A TEMPERATURE RANGING FROM ABOUT 600*F. TO ABOUT 1000*F.; AT A LEVEL IN SAID WELL SUBSTANTIALLY OPPOSITE SAID FORMATION WITH SUFFICIENT OXYGENCONTAINING GAS TO PRODUCE PRODUCTS FROM THIS PARTIAL OXIDATION, PASSNG SAID PRODUCTS IN INDIRECT HEAT EXCHANGE RELATION WITH AN OXYGEN-CONAINING MIXTURE OF A FLUID HYDROCARBON HICH IS TO BE SUBSEQUENTLY PARTIALLY OXIDIZED IN SAID REACTION ZONE TO PREHEAT SAID MIXTURE, WITHDRAWING SAID PRODUCTS FROM AID ZONE AND HEATING SAID FORMATION THEREWITH, AND SUBJECTING SAID MIXTURE TO PARTIAL OXIDATION, SAID MIXTURE HAVING SUFFICIENT OXYGEN TO PRIDUCE PRODUCTS WITHIN THE AFORESAID TEMPERAURE RANGE. 